docs: def canonical_names(self):
          """Figure out which canonical names clients will access this service.
          """
          cns = []
          for r_id in relation_ids('identity-service'):
              for unit in related_units(r_id):
                  rdata = relation_get(rid=r_id, unit=unit)
                  for k in rdata:
                      if k.startswith('ssl_key_'):
                          cns.append(k.lstrip('ssl_key_'))
  
          return sorted(list(set(cns)))